class Solution {
public:
    bool isSameTree(TreeNode* p, TreeNode* q) {
        if (p == nullptr && q == nullptr)
            return true;
        else if (p == nullptr || q == nullptr)
            return false;
        else
        {
            if (p->val == q->val)
                return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
            return false;
        }
    }
};